The electric power converter converts power into the predefined power by creating electromagnetic induction by switching on and off in a coil. The PWM (pulse width modulation) is utilized for the electric power conversion of the electric power converter. For example, in case that the converter enlarges the output power, the on time width is set to be long, in case that the converter lowers the output power, the on time width is set to be short.
However, when the input power becomes low, the inductive voltage or the inductive current is not induced. Therefore, the predetermined output power is not created. Therefore, the control device discloses in which, when the input power becomes low, the control device switches the big power conditioner to the small power conditioner to keep the inductive current normal (Patent Document 1).    Patent Document 1: Japanese Laid-open Patent Publication No. 2009-225489.
However, when the power conditioner is switched by the input power, the power conditioner is activated or deactivated by the fluctuation of input power, and thereby, the behavior of power conditioner is possible to become unstable.
To solve the above problem, according to an aspect of the invention, the object of an aspect of the embodiment to provide an electric power converter that sets the minimum value of pulse width at the value (for example, 30%) that causes the power converter inefficient, and shorter the period to set the power of power converter at the power that is higher than the power of one PWM output, thereby, do not cause the efficiency power converter lowering.